Protective system for walls of buildings or containers

ABSTRACT

A protective system protects a wall of a building or container from impact loads. The protective system has a buffer layer which is arranged on the impact side of the wall of the building or container and absorbs the impact energy of the impact load predominantly by plastic deformation. The buffer layer contains a deformation lattice which is formed by a substantially regular arrangement of unit cells and has a number of lattice layers and the intermediate spaces in which are filled with a deformable damping material. Each of the unit cells is composed of a plurality of lattice struts which form the edges of a pyramid.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation application, under 35 U.S.C. §120, of copending international application No. PCT/EP2011/006377, filed Dec. 16, 2011, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent application No. DE 10 2011 008 067.8, filed Jan. 7, 2011; the prior applications are herewith incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a protective system against impact loads for building walls or container walls which is preferably also suitable for retrofitting to pre-existing building walls or container walls.

In principle, when planning a structure or designing a container, consideration is given not only to the intrinsic loads and the intended imposed loads but also to the temporarily occurring additional loads which are to be expected, such as, for example, snow loads, ice loads, wind loads and also impact loads. Moreover, in some cases, for example owing to changed regulations or standards, there occurs a subsequent overhaul of the structure or the container. In these cases, it is ensured, for example, by extensions or conversions that the structure or the container can overcome further loads beyond the originally planned loading limit.

In this connection, the term impact loads embraces all events in which an accelerated mass collides with a structure or a container. In the case of structures or containers for civilian use, these impact loads are caused especially by objects accelerated by gusts of wind and by inappropriately driven motor vehicles. If, by contrast, the structure or the container is viewed as a military target by potential aggressors, account should also be taken of impact loads which are caused, for example, by projectiles or guided missiles.

At the present time, structures or containers are protected from high-energy impact loads primarily by using simple and massive steel plates or reinforced concrete slabs. A disadvantage here is the high intrinsic weight and the large dimensions of the plates or slabs.

BRIEF SUMMARY OF THE INVENTION

Taking this as the starting point, the invention is based on the object of developing a weight and/or dimension-reduced system or construct by which structures and transport containers can be protected in particular against high-energy impact loads.

A protective system corresponding to the teaching of the invention acts as protection against impact loads for an individual building wall, a complete building, an individual container wall or a complete container. It is provided for this purpose to arrange a buffer layer on the impact side of the region to be protected, which buffer layer absorbs the impact load-induced kinetic energy predominantly by plastic deformation. The basic framework or skeleton of the buffer layer is formed by identical elementary cells which are composed of lattice struts and which are substantially regularly arranged and thus completely cover the region to be protected as a deformation lattice. Consequently, the basic structure of the buffer layer, which is formed from at least one layer of these elementary cells, has a crystal-shaped base structuring. The shape of an individual elementary cell is pyramid-like, with the lattice struts forming the edges of the pyramid shape. The basic framework is supplemented by a deformable deformation material which fills the intermediate spaces in the deformation lattice and as a result completes the buffer layer.

An embodiment in which the lattice struts of an elementary cell form a regular pyramid is preferred since, as a result of this design of the basic framework, both an advantageous deformability is achieved and a simple technical implementability is ensured. In this connection, it is also expedient if the base of the pyramid shape is quadrilateral and in particular square.

Furthermore, it is considered to be advantageous if the deformation lattice has at least two, but preferably four to eight, lattice layers composed of elementary cells since, with an increasing number of lattice layers, the maximum impact energy which can be absorbed increases. On the other hand, of course, the thickness and the intrinsic weight of the protective system also increase with an increasing number of layers. In the case of eight lattice layers, simulation calculations show that even large and heavy projectiles with a high flight speed are securely stopped within the buffer layer and do not penetrate as far as the underlying building wall or container wall.

If a plurality of lattice layers is present, it is additionally advantageous if in each case two lattice layers situated directly above one another are arranged laterally displaced with respect to one another by half the length of the diagonals of an elementary cell base in the direction of the diagonals. Thus, in brief, the lattice layers situated directly above one another are displaced diagonally with respect to one another by half an elementary cell. This results in an alternating stack sequence ABAB in which the apexes of the pyramids forming the lower lattice layer bear on the corners of the bases of the pyramids forming the lattice layer situated above. X-shaped strut arrangements formed as a result serve as additional reinforcing elements in the deformation lattice.

The material used for the lattice struts is preferably highly ductile steel. This is obtainable in the widest variety of specifications, resulting in a good degree of variability which allows adaptation of the properties of a buffer layer according to the invention to various specifications or standards.

It is conceivable in principle to connect the lattice struts to one another solely with the aid of the deformation material and to keep them in their relative positions with respect to one another. However, in a preferred embodiment, the lattice struts of an elementary cell and also the elementary cells and lattice layers among one another are in each case fixedly connected to one another, that is to say for example screwed, adhesively bonded or welded, with the result that the basic framework on its own account already constitutes a construction which can absorb impact energy by plastic deformation.

If the buffer layer is also to function, for example, as building protection against striking missiles, it is expedient to provide for an elementary cell a lateral extent of approximately 0.5 m to 4.0 m and a height extent, which is not necessarily identical thereto, of 0.5 m to 4.0 m. In this case, correspondingly cut-to-size square or round steel with an edge length or a diameter of approximately 10 mm to 50 mm is used for the lattice struts.

According to a further preferred embodiment, concrete, in particular so-called foamed concrete or lightweight porous concrete is used as damping material. Foamed concrete is a concrete which is planned to have an increased air pore content of generally >30 percent by volume which is usually produced by adding a foam former or by mixing in prefabricated foam. This material can on the one hand absorb large pressure forces and is on the other hand comparatively light (low density) and readily flowable. In addition, it has good thermal insulation properties. Fibers, for example of steel or plastic, are preferably additionally admixed with the concrete or foamed concrete that is used in order to increase its ductility and hence, with respect to the buffer layer, its effectiveness. Details on this type of material can be found in the literature under the keyword “UHPC” (Ultra High Performance Concrete).

Moreover, it is advantageous if the buffer layer terminates on the impact side with a cover layer, for example of steel or a composite material, in particular a fiber composite material. In the case of a pointed or sharp-edged impact body, this serves in particular to better distribute punctiform pressure surges over a larger region of the deformation lattice and hence to increase the effective impingement area. During the erection of the protective system, the cover layer can also serve as shuttering when casting the damping material.

It is considered to be very expedient in this context to fasten the cover layer to the buffer layer with the aid of anchor elements since, for example, a simple exchange can take place as a result. Alternatively, however, it is also conceivable to adhesively bond the cover layer to the buffer layer over a large area.

A protective system according to the invention is primarily configured as protection for planar surfaces. Accordingly, it is advantageous to select an arrangement of the elementary cells in which the bases of the elementary cells of each lattice layer are situated in a common plane and in which these planes are oriented parallel to the surface of the building wall or container wall to be protected. Notwithstanding, it is also possible to adapt the buffer layer to curved surfaces (for example cupolas, domes, cylinders and the like). For this purpose, either the deformation lattice is distorted to correspond to the curvature or a modified deformation lattice with a modified lattice structure is used.

The advantages achieved by the invention consist in particular in that, by a composite structure composed of a three-dimensional, lightweight, highly deformable (ductile) and preferably multi-layer spatial bar-type supporting structure and a cast damping material, there occurs a particularly good conversion of the kinetic energy of impact loads (for example aircraft, whirlwind-inducted projectiles, pressure waves) into plastic deformations of the supporting structure, wherein the damping material acts as a stabilizing matrix with a very high degree of damping. Impact energy is additionally absorbed by the nonlinear deformation and squashing of the damping material preferably produced from fiber-reinforced foamed concrete (fiber foamed concrete). By contrast with conventional solutions in which impact protection is achieved by an increased stiffness (greater wall thickness) and an increased reinforcement content (for example shear reinforcement, reinforcement connectors) of the reinforced concrete components in question, in the case of the impact protection system according to the invention the generation and propagation of vibrations, oscillations and elastic waves is significantly suppressed or damped and kept away from the object or structure to be protected.

Consequently, additional protection against seismic loading is also ensured. This is because seismic excitations or jolts are likewise effectively damped.

The protective system according to the invention can be erected simply and quickly, in particular using preassembled units of the deformation lattice which are installed in layers on the object to be protected and then cast with the damping material. Retrofitting of existing wall structures is possible.

The protective system according to the invention is particularly advantageously used in buildings of nuclear plants, in particular nuclear power stations, but also in conventional power stations and chemical plants, and also in transport containers for nuclear or chemical materials and waste.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a protective system for walls of buildings or containers, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagrammatic, perspective view of an elementary cell of a buffer layer according to the invention;

FIG. 2 is a diagrammatic, perspective view of a lattice layer of a deformation lattice of the buffer layer according to the invention;

FIG. 3 is a perspective, partially sectional view of the buffer layer according to the invention on a partially represented building roof; and

FIG. 4 is a plan view of a section of a deformation lattice.

DESCRIPTION OF THE INVENTION

Parts corresponding to one another are provided with the same reference numbers in all the figures.

Referring now to the figures of the drawings in detail and first, particularly to FIG. 3 thereof, there is shown in an exemplary embodiment, a subsection of a building roof 1 which is observed by way of example. A planar outer surface 2 of the subsection is intended to be protected against impact loads by retrofitting. For this purpose, a buffer layer 3 is positioned on the surface 2. Here, the buffer layer 3 is fixed on the surface 2 with the aid of an integrally bonded connection (not shown in further detail) or in some other way.

A construction of welded-together lattice struts 4 serves as a base for the buffer layer 3. It should be pointed out again at this point that the type of nonreleasable connection between the lattice struts 4 is not restricted to those selected here. Connections by screwing, riveting, clamping or adhesive bonding are considered as alternatives which are likewise expedient. In each case eight of these lattices struts 4 of cut-to-size round steel form an elementary cell 5 represented in FIG. 1. According to their spatial arrangement, the lattice struts 4 of an elementary cell 5 form the edges of a straight pyramid with a square base. The ratio between the edge length of the square base and the height of the pyramid is approximately 1.7 in this case example.

A crystal-like deformation lattice is formed by a regular arrangement of the elementary cells 5 and the nonreleasable connection of these elementary cells 5 with one another. The deformation lattice is, as it were, built up from a plurality of lattice layers 6 which are layered above one another in the stacking direction 7. The arrangement of the elementary cells 5 within each lattice layer 6 is in this case configured such that the square bases of the elementary cells 5 bear against one another in a gap-free manner as in a checker-board, with the result that the lowermost lattice layer 6 in the stacking direction 7 completely covers the planar surface 2 to be protected. A schematic representation of the arrangement of a lattice layer 6 can be seen in FIG. 2.

Two lattice layers 6 situated directly above one another are arranged laterally displaced with respect to one another by half the length of the diagonals of an elementary cell base in the direction of the diagonals. Owing to this alternating stacking sequence ABAB, the apexes of the pyramids forming the lower lattice layer 6 make contact with the corners of the bases of the pyramids forming the above-lying lattice layer 6. It is precisely at these contact points that the individual lattice layers 6 are nonreleasably connected, i.e. welded, to one another. At the same time, additional X-shaped strut arrangements 8 are produced in this way. In a similar manner to a crane boom or a steel bridge construction, they serve as additional reinforcing elements in the deformation lattice. The X-shaped strut arrangements 8 can be seen when viewing the deformation lattice in profile. A corresponding section is shown in FIG. 4.

In the case of the buffer layer 3 according to the invention, the deformation lattice acts in the manner of a basic framework or skeleton. This basic framework is enclosed by a damping material 9 made from a fiber-reinforced foamed concrete. The foamed concrete supplements the deformation lattice to give a parallelepipedal buffer layer 3 and at the same time fills the intermediate spaces in the deformation lattice.

Both components, the damping material 9 and the deformation lattice, can absorb impact energy on their own account. While in the deformation lattice this takes place predominantly by plastic deformation, the energy absorption in the case of the damping material 9 acts primarily by compression. However, by combining both components to form the buffer layer 3, the absorption capacity, exactly like the damping capacity with respect to pressure waves or oscillations, of the individual components is excelled. 

1. A protective system for protecting a wall of a building or container from impact loads, the protective system comprising: a buffer layer disposed on an impact side of the wall of the building or the container and absorbs an impact energy of an impact load predominantly by plastic deformation, said buffer layer containing: a deformation lattice formed by a substantially regular configuration of unit cells forming a number of lattice layers; a deformable damping material filling intermediate spaces in said deformation lattice, said deformable damping material being a fiber-reinforced foamed concrete; and each of said unit cells composed of a plurality of lattice struts forming edges of a pyramid.
 2. The protective system according to claim 1, wherein said pyramid formed of said lattice struts of a unit cell is a regular pyramid.
 3. The protective system according to claim 2, wherein said pyramid formed of said lattice struts of said unit cell has a rectangular base.
 4. The protective system according to claim 1, wherein at least two of said lattice layers are provided for said deformation lattice.
 5. The protective system according to claim 1, wherein in each case two said lattice layers disposed one directly above the other are disposed laterally offset from one another by a half length of a diagonal of a base of said unit cell in a direction of a diagonal.
 6. The protective system according to claim 1, wherein said lattice struts are made of steel.
 7. The protective system according to claim 1, wherein said lattice struts are rigidly connected to one another at contact points thereof.
 8. The protective system according to claim 1, wherein each of said unit cells has a lateral dimension of approximately 0.5 m to 4.0 m and a vertical dimension of approximately 0.5 m to 4.0 m.
 9. The protective system according to claim 1, wherein said buffer layer has a cover layer on an impact side.
 10. The protective system according to claim 9, wherein said cover layer is made of a material selected from the group consisting of steel and a composite material.
 11. The protective system according to claim 9, wherein said cover layer is attached to said buffer layer by means of anchoring elements.
 12. The protective system according to claim 1, wherein bases of said unit cells of each of said lattice layers are disposed in a common plane, and wherein the common plane is disposed parallel to a surface of the wall of the building or the container.
 13. The protective system according to claim 2, wherein said pyramid formed of said lattice struts of said unit cell has a square base.
 14. The protective system according to claim 1, wherein four to eight of said lattice layers are provided for said deformation lattice.
 15. The protective system according to claim 1, wherein said lattice struts are rigidly welded to one another at the contact points thereof.
 16. A building, container or industrial plant, comprising: a wall; a protective system disposed on said wall at least in regions in an expected impact region, said protective system containing: a buffer layer disposed on an impact side of said wall and absorbs an impact energy of an impact load predominantly by plastic deformation, said buffer layer containing: a deformation lattice formed by a substantially regular configuration of unit cells forming a number of lattice layers; a deformable damping material filling intermediate spaces in said deformation lattice, said deformable damping material being a fiber-reinforced foamed concrete; and each of said unit cells composed of a plurality of lattice struts forming edges of a pyramid. 